Utilization of a very small anomalous diffraction signal provided by sulfur atoms of the cysteine and methionine residues or by phosphorus atoms of nucleic acids, intrinsically present in all proteins or RNA/DNA can be successfully used to solve crystal structures of proteins. This approach, in part pioneered by us, is currently gaining increasing popularity and becomes a routine technique in the practice of macromolecular crystallography. The diffraction data to extremely high resolution in the range of 0.55-0.7 angstrom were measured using synchrotron radiation from crystals of oligonucleotides and oligopeptides, and the refined models revealeed the unprecedented structural details of the investigated molecules including electron densities at the sigma bonds between atoms. The observed very fine features in this structures will serve to improve the stereochemical libraries used for routine refinement of protein crystal structures at lower resolution. We participated in several collaborative structural projects on various biologically important proteins, such as fluorescenty proteins used as biomarkers, human mitochindrial helicase, rhizobium fucosyltransferase and plant S-adenosyl-homocysteine hydrolase.